Optimizing the nonlinear operator in backward propagation

Backward propagation is the most effective way of performing digital post-compensation in an optical system. In this work we exploit a simple optimization procedure based on finding the optimal fraction of nonlinearities that must be compensated in order to achieve the best performance. Using a 40 Gb/s NRZ-QPSK signal, propagated over 20 × 80 km of standard single-mode fiber, we present compensation results employing nonlinear optimization and we compare its performance with non-optimized backward propagation. Finally, we analyze the impact of both temporal and space resolution on the optimum nonlinear operator and on the overall compensation performance.